Alkylation of aromatics



ALKYLATION OF AROMATICS William Judson Mattox and William Floyd Arey,Jr.,

Baton Rouge, La., assignors to Esso Research and Engineering Company, acorporation of Delaware Application January 29, 1957, Serial No. 636,9096 Claims. (Cl. 260-671) The present invention relates to the productionof alkyl aromatic compounds by reacting aromatic and olefinichydrocarbons. More particularly, the present invention relates to aprocess for the production of alkyl aromatic hydrocarbon compounds ofhigh anti-knock value, which are of suitable boiling range for use asmotor fuels. Still more particularly, the present invention relates to anovel catalytic composition peculiarly adapted to produce high yields ofalkylated aromatics.

Processes for the cracking of gas oil and similar petroleum fractions togasoline result in the production of normally gaseous hydrocarbons suchas ethylene, propylene, the butylenes and higher. Appreciable quantitiesof naphtha fraction product are also olefinic, and have relatively highoctane values. However, with the increasing development of highcompression engines, these fuels are not satisfactory from ananti-detonation viewpoint.

Alkylated aromatics boiling in the naphtha range are known to becapable, when added to naphthas boiling in the gasoline fraction, ofimparting a high degree of anti-knock capability. Various methods forthe production of alkylated aromatics by combining olefinic or similarunsaturated material, either from products of a conventional thermal orcatalytic cracking process or from other sources, with aromaticcompounds such as benzene or its homologues, have been proposed.

The prior art processes in general employ an acidic catalyst. Thealkylating agent is most frequently an alkyl halide, an alcohol, or analkene; the essential requirement is that the alkylating agent becapable of inter acting with the catalyst to produce a carbonium ion.The catalyst is a powerful electrophilic reagent, in the Lewis sense,such as AlC1 FeCl SbCl BF ZnCl TiCl HF, H2804, H3PO4, SiO Al O P205 andthe like. These reactions are generally carried out at low temperaturesand in particular when a Friedel-Crafts catalyst is employed, in thepresence of a hydrogen halide such as HCl.

The prior art processes carried out with acidic catalysts are open tomany objections. Beside the corrosive nature of the catalyst, thecatalyst consumption is high as are regeneration costs, and yields ofalkylate boiling in the gasoline range are low, and complicatedseparations and recycle of feed are required. Furthermore, thesecatalysts tend to polymerize the olefinic reagents and thus minimizeavailable starting materials. 7

It is an object of the present invention to provide a highly eflicientprocess for the production of alkyl aromatic compounds.

It is a still further object of this invention to employ a non-acidiccatalyst for alkylating aromatics with olefins which provides optimumyields of alkylated aromatics boiling within the naphtha boiling rangeand minimizes the formation of higher boiling compositions.

Other and further objects and advantages of the present invention willbecome more clear hereinafter.

nited States Patent 0 2,904,607; Fatented Sept. 15, 1959 It has now beenfound that aromatic may be particularly readily alkylated with olefinsby contacting the reagents at moderately elevated temperatures with acrystalline alumino-silicate catalyst having pore openings adequate toadmit freely the individual aromatic and olefinic molecule, and whichcatalysts have a basic rather than the hitherto desired acidic reaction.The pore opening will therefore be about 6 to 15 Angstroms. Too large anopening, however, does not permit the high activity because of theconcomitant decrease in available surface area.

Alumino-silicates of high alkylation activity may be prepared by mixingand heating sodium aluminate and sodium silicate, preferablymetasilicate, under carefully controlled conditions to produce acrystalline product which is subsequently dehydrated under condition topreserve the crystalline structure. The sodium content of thecrystalline aluminosilicate may be replaced by effecting ion exchangewith an appropriate metal salt such as a group II, 111 or IV metal. Themetal ion influences the size of the pore openings, as does the ratio ofthe reagents and the reaction conditions.

In accordance with the present invention, the alkylation catalyst isprepared from a sodium silicate having a high ratio of soda to silica.The ratio is at least 0.8/1, and may be as high as 2/1. Preferably,however, the ratio is 1/ 1, and the desired reagent is sodiummetasilicate. Water glass or sodium silicates having lower Na O/siOratios do not form the adsorbent crystals unless subjected to extendedheat soaking or crystallization periods.

The composition of the sodium aluminate is less critical than that ofthe sodium silicate. Sodium aluminates having any ratio of soda toalumina in the range of 1/1 to 3/1 may be employed; however, a sodiumaluminate having a high ratio of soda to alumina is preferred, and asodium aluminate having the ratio 1.5/1 Na O/Al O is particularlydesirable. The amounts of sodium silicate solution and sodium aluminatesolutions are such that the ratio of silica to alumina in the finalmixture is at least 3/1 and preferably about 4/ 1l0/1. The method ofmixing the sodium metasilicate and sodium aluminate solutions must becarried out in a manner allowing formation of a precipitate having auniform composition. A preferred method is to add the sodium aluminateto the sodium metasilicate at ambient temperatures using rapid andefficient agitation to make a homogeneous paste. Thereafter the mixtureis heated to about 180-215 F. for a period as long as 200 hours or moreto ensure crystallization in the crystal form necessary to adsorbaromatic molecules. It has been found that the heat soaking period isessential to produce the desired product, which has a pore opening ofabout 13 Angstroms.

The process of preparing the catalyst may be more clearly understoodwhen read in conjunction with Figure 1, which is a diagrammaticrepresentation of a preferred method of manufacturing the large porematerial. Turning now to that figure, a solution of sodium metasilicateis prepared in vessel 2 and of sodium aluminate in vessel 4. Theconcentration of the silicate may be in the range of about 30-300 gramsof SiO per liter, preferably in the range of about 200 grams per liter.The solution of aluminate has a concentration in the range of 40400grams A1 0 per liter, preferably about 200-300 grams per liter. Theamounts of metasilicate and aluminate solutions employed are such thatthe ratio of silica to alumina in the final mixture is in the range of3/ 1-10/ 1. A ratio of about 4/ l-8/ 1 is particularly desirable.

Sodium aluminate solution comprising 5-25 A1 0 is passed via line 1 intoa mixing zone 5 where it is contacted with a sodium silicate solutioncomprising -25% SiO as solid, introduced through line 3. The mixing zoneis preferably maintained at ambient temperatures. Mixing should be rapidand efiicient, e.g., the impeller zone of a centrifugal pump. Therelative amounts of silicate and aluminate introduced to the mixing zoneis about 3.5/1 ratio SiO /Al O The resulting mixture, or slurry, is thenfed via line 7 through a heat exchanger 9 which is maintained at about180 F. to 250 F. or higher. The heat exchanger may comprise water, orsuperheated steam, or high boiling organic materials, or heated fluidsolids, at controlled temperature. During the time of passage throughthe heated zone, the slurry undergoes crystallization to give thedesired adsorbent structure. The flow rate of the material through line7 is adjusted so that the time interval spent in the heated zone 9 issulficient to complete crystal formation. At about 210 F., this is about3 to 24 hours; at higher temperatures, shorter times are required, whileat lower temperatures, somewhat longer time is required. The effluentcrystalline product is then taken via line 11 to a filter and subsequentfinishing operations. If desired, a portion of the efiluent stream fromthe heated zone may be recycled via line 13 by a pump (not shown) toslurry line 7 to serve as seed material and possibly catalyst for thecrystallization process.

The precipitated sodium-aluminosilicate, after the heatsoaking period,is withdrawn through line 11, passed to filtration and water-washingzone 17, and then dried and activated in calcination zone 15. Activationtemperature may be in the range of 4001000 F., preferably about 700900F.

The process of manufacture may be modified in various ways, providingthe critical features of the high ratio of Na O/SiO in the sodiumsilicate and of the high ratio of SiO /Al O and the heat soaking periodare maintained. Thus, it may be desirable to base-exchange the recoveredzeolite with another ion, such as calcium, to form a calcium sodiumalumino-silicate. This baseexchange modifies the size of the poreopenings. Where this is done, the filter cake of sodium alumino-silicatemay be base-exchanged with a solution of a calcium salt or other saltsolutions before drying, though this is not essential. The crystallineprecipitate of sodium alumino-silicate may be dried, activated byheating to about 700 to 900 F. and used as such, or if desired, thedried alumino-silicate may be base-exchanged with a salt solution.

The exchange reaction may be carried out in several stages if desiredusing a column contacting technique, countercurrent flow, or other knownmethods of carrying out base exchange reactions. If desired, very dilutesolutions of calcium salt, for example 0.01 to 0.1 molar, may beemployed for the base exchange reaction; however, it is preferred to usemore concentrated solutions, for example, in the range of about 0.5 to3.0 molar. A solution of calcium chloride having a concentration in therange of about 5 to 20 percent by weight is particularly preferred.

Base exchanging may be carried out by treating the wet precipitate inthe filter with a salt solution, or by reslurrying the precipitate in asalt solution. Besides sodium, other alkali aluminates and metasilicatessuch as potassium, lithium and the like may be employed. Similarly,other water soluble salts may be employed in the base exchange reactionin place of calcium salts. For example, salts of potassium, lithium,strontium, magnesium, zinc, cadmium, and the like may be employed.Magnesium is particularly desirable.

The alkylation reaction is carried out in equipment of conventionaltype, one arrangement of which is illustrated in Figure 2. An aromatic,such as benzene or an aromatic concentrate is fed through line 2 alongwith .a gaseous olefin to a reactor 6 packed with the aluminosilicatecatalyst and maintained at a temperature within the approximate range of300 to 850 F., preferably 400 to 750 F., and at a pressure which mayvary up to about 1000 p.s.i.g. The reaction product is passed throughline 8 to gas separator 10 for recovery of unconverted olefins which arerecycled via 12 to the alkylation reactor. Liquid product from thisseparator is transferred to a distillation column 16 for separation ofunconverted aromatics, mono-alkyl aromatics, and any poly-alkylaromatics formed. The unconverted aromatics fraction is recycled via 18to the alkylation reactor while the mono-alkylated'aromatics arerecovered as product. Poly-alkyl aromatics, such as the di-alkylaromatics, will be recycled to the alkylation reaction if the yield ofmono-alkyl aromatics is to be maximized, since these more highlyalkylated products react with benzene in the presence of thealumino-silicate catalyst to form additional quantities of themono-alkyl aromatic. One of the distinct advantages, therefore, to theuse of the alumino-silicate catalyst is the formation, under normaloperating conditions, of a high proportion of the mono-alkyl derivative.If, however, it is desired to maximize poly-alkyl aromatics production,the monoalkyl aromatic may be recycled to the reactor along with theunconverted aromatic while the poly-alkyl aromatics are recovered asproduct. When producing monoalkyl benzenes, the aromatic/ olefin molratio will preferably be about 1/1 to 10/1. If poly-alkyl aromatics aredesired, the ratio is preferably about 0.5/1 or less.

In addition to the advantages already mentioned for the alumino-silicatecatalyst, the adaptability of this catalytic material to various modesof contacting is outstanding in comparison with previously knowncatalysts. For example, the alumino-sil-icate may be used in fixedbed ormoving-bed reactors, as pellets or various shaped forms, as a fluidizedpowder, or as a powder dispersed or suspended in the liquid hydrocarbonor in some suitable fluid. Further, the alumino-silicate not only ischaracterized by long life but is completely restored in activity afterprolonged use by simple oxidation treatments with air or otheroxygen-containing gas. The usual high catalyst losses and/or expenseresulting from reworking of conventional acid type catalysts is avoided.

The process of the present invention may be further illustrated by thefollowing example.

A crystalline sodium alumino-silicate having a pore opening of about 13Angstroms, and prepared in a manner similar to that described heretoforewas employed as an aromatic alkylation catalyst. The sodiumaluminosilicate was prepared in aqueous medium at a final pH of 1012,and even after drying and calcining at 850 F. an aqueous suspensionshowed a pH .of 10-11, indicating the basic nature of this catalyst.

EXAMPLE 1 Alkylation of benzene with propylene sodium alumina-silicatecatalysts [Temp-400 F.; pressure-atm.; CuHG/CaHo mo1ratio1.5/1]

Test N0 1 2 Alumino-Silicate Catalyst:

Pore Opening, A Composition Reaction Product:

Isopropylbenzene, Vol. percent Polyisopropylbenzene, Vol. percenL.

Alkylate: Isopropylbenzene, Vol. percent Polyisopropylbenzene, Vol.percent" These data show clearly that it is not enough to employ azeolite for the alkylation catalyst, but a zeolite having pore openingslarge enough to admit the reactants. A 4 Angstrom pore opening is toosmall for this purpose and thus no product was obtained. On the otherhand, with the 13 Angstrom pore openings, 83% of the alkylation productthat was obtained was mono-alkyl aromatic. To produce alkylated productcontaining this high a percentage of cumene with phosphoricactivated-kieselguhr catalyst (900 p.s.i., and 525 F.) requires abenzene to propylene mol ratio of 4/ l and a correspondingly highrecycle of benzene.

EXAMPLE 2 A 500 gram sample of the 13 Angstrom pore diameter sodiumzeolite was slurried in a liter of water and 1500 cc. of magnesiumchloride solution added. The base exchange operation was repeated twicewith fresh 12% magnesium chloride solution each time. The wet pelletswere dried in an oven at 250 F. and calcined for 4 hours at 850 F. Thismaterial when analyzed showed that about 76% of the original sodacontent was replaced with magnesia.

The magnesium zeolite thus formed was tested for alkylation activity bycontacting with propylene and toluene mixtures at 850 F. at atmosphericpressure. Feed rates were about 0.64 v./v./hr. for the toluene and about5 mol propylene per mol of toluene feed. The results were as follows:

Liquid product, C 4- Mol percent toluene 69.3 Mol percent C C Caromatics 17.7

These data show that the magnesium form of this zeolite is also anactive alkylating agent for aromatics with olefins.

Not only may aromatics be alkylated in accordance with the presentinvention, but also isoparaflins and alicyclic compounds. Thus,isobutane and isopentane may be alkylated with propylene or isobutylene.

It is also advantageous to employ these 13 Angstrom porealumino-silicates for concentrating aromatics or isoparaifins fromhydrocarbon streams. For example, the alumino-silicate may be used toconcentrate the aromatic reactant from such materials as straight run,thermal or catalytic naphthas in which the aromatic content is usuallyquite low, and hence these streams could not normally be used asalkylation feeds. Aromatics for the alkylation can similarly be adsorbedfrom hydroformates or aromatized naphthas. Olefinic reactants maylikewise be concentrated from a variety of feed sources.

What is claimed is:

1. A process for alkylating an aromatic hydrocarbon with an olefin whichcomprises contacting the same in the presence of a crystalline metallicalumino-silicate having a uniform pore opening of about 6 to 15 Angstromunits at a temperature of from about 300 to 850 F.

2. An improved process for alkylating aromatic hydrocarbons with olefinswhich comprises passing an olefinic stream to an alkylation zone,contacting said reactants with a crystalline metallic alumino-silicatehaving uniform pore openings of 13 Angstroms at about 400 to 750 F., andrecovering good yields of alkylated aromatics from said zone.

3. An improved process for preparing a high octane motor fuel whichcomprises passing an aromatic hydrocarbon having from C to C carbonatoms and a low boiling olefin to an alkylation zone, contacting saidmixture at a temperature of from about 400 to 750 F., with a metalliccrystalline alumino-silicate catalyst having uniform pore openings of 13Angstroms, forming a reaction product comprising monoalkylated andpoly-alkylated aromatics, separating a high octane gasoline comprisingsubstantial amounts of monoalkylated aromatics, and recyclingpoly-alkylated aromatics to said alkylation zone.

4. The process of claim 3 wherein said catalyst is a sodiumalumino-silicate.

5. The process of claim 3 wherein said catalyst is a magnesiumalumino-silicate.

6. The process of claim 3 wherein said aromatics are concentrated from adilute aromatics comprising stream by contacting said stream with saidalumino-silicates.

References Cited in the file of this patent UNITED STATES PATENTS1,728,732 Jaeger Sept. 17, 1929 2,197,862 Hyman Apr. 23, 1940 2,253,285Connolly Aug. 19, 1941 2,294,779 Hyman 'Sept. 1, 1942 2,317,803 Reeveset al Apr. 27, 1943 2,698,305 Plank et a1. Dec. 28, 1954

1. A PROCESS FOR ALKYLATING AN AROMATIC HYDROCARBON WITH AN OLEFIN WHICHCOMPRISE CONTACTING THE SAME IN THE PRESENCE OF A CRYSTALLINE METALLICALUMINO-SILICATE HAVING A UNIFORM PORE OPENING OF ABOUT 6 TO 15 ANGSTROMUNITS AT A TEMPERATURE OF FROM ABOUT 300* TO 850*F.